Wing and legs?

Well, my 2 month old chicks have this habit. When I remove the botton tray(which hold the poop)(it has wire above it) and I put the chicks on the grass my chicks spread out their wings far and sit down. And when they sit, one kinda shakes it butt and then sits. When they sit, they kinda tilt with 1 of their legs sticking out. The wing covers this leg when tthey do this. They only do this on the grass Why???
Is it normal?

Though I certainly know where you're coming from. Our first chicks were raised in through the winter in the basement. when we finally took them out to a real coop, one started sunnign and I got quite conserned. Picked her up, baby-ed her, set her down. Took me a little while to figure things out.